This invention relates to telecommunications conference call systems and to methods for operating them in order to balance loads across multiple conference bridges.
A conference call service works by connecting multiple telephones through a common carrier switch to ports on a bridge that mixes the audio signals coming from such telephones and sending the result back out through the common carrier switch to those telephones. One common way of operating a conference bridge is to have all participants place outgoing calls from their telephones into the conference call system, and then to have each participant enter a specific access code to signify the conference it is desired to join.
In a large scale system, the conference call service provider typically makes use of a large number of conference bridges. All callers participating in the same conference call, however, need to be placed on the same bridge. This means that the common technique of having incoming calls hunt across all bridges for an available port does not work for conference call systems. Because each conference call is not independent of the others, it must be placed on the same bridge with all other calls in the same conference.
In a conference call system with multiple bridges, what is required is selection of a particular bridge to be used for a particular conference call and connection of each incoming caller to the designated conference on the designated bridge so that:
1) Each customer can maintain a fixed telephone number to call and an access code to use that remains the same for all of his conference calls over time.
2) The system and conference call service provider can change the specific bridge that any customer uses for conference calls from time to time. This may be done, for example, when the conference call service provider adds more bridge capacity to its system, or when capacity is reduced when bridges go out of service because of hardware or software problems or because of maintenance.
3) The system can balance conference call loads across multiple conference bridges. If conference A is unexpectedly large, or continues for an unexpectedly long time, then a bridge which had been anticipated to become available for conference B may be busy at the time conference B is scheduled to begin. If another bridge has capacity available at this time, then the conference call service provider should be able to dynamically place conference B on a bridge that has sufficient available resources.
One common approach to schedule conference calls is to give each customer who makes a conference call reservation or request a telephone number and an access code at the time the reservation or request is made. The telephone number provides access to a specific bridge and, if that bridge is out of service at the time of the call, then the customer must use a different phone number to access a different bridge.
In order to give customers the same phone number for every reservation or request they make, each customer can be assigned to a specific bridge. Bridge hardware must be very fault tolerant, which adds to its expense, and load balancing must be done, e.g., by assigning each new customer to the most lightly loaded bridge. Such a method of load balancing is very crude, however, and there is no easy way to deal with an unexpected situation when all the customers assigned to the same bridge decide to request a conference call scheduled to begin at the same time. In this instance, the bridge in question may run out of port capacity, even if other bridges in the system happen to be free.
Another known approach to solving the problem is to implement an inter-bridge connection so that all the bridges in a conference call system are connected together. This allows incoming calls to terminate on any of the bridges in the system and to be routed over the inter-bridge connection to the appropriate bridge. Any bridge can terminate the call and prompt for the participant access code. Once the access code has been received and verified, the system can determine which of the bridges the conference is being held on and route the call to that bridge using the inter-bridge connection. A disadvantage of this approach is that it requires additional hardware to connect the bridges. This hardware adds to the expense and provides additional ways in which the system can fail.
A third approach to solving the problem is to connect all the bridges in the conference call system to the public switched telephone (PSTN) network through a large, special-purpose switch such as a private branch exchange (PBX) instead of connecting directly to the carrier""s equipment in such a way that all calls come in through this switch, and this switch can be controlled by the system to route calls to the appropriate bridge. The disadvantage of this approach is that for each bridge port of capacity, the conference call service provider must also purchase and install two additional ports on this switch: one to connect to the bridge, and another to connect to the carrier. Adding this switch is expensive and may introduce another point of potential failure.
In accordance with the invention, a conference call system receiving calls through a common carrier switch, where the conference call system comprises at least two multi-port conference bridges is operated by: accepting a conference call request for n participants, where n is an integer greater than unity, and assigning a conference access code for the request; selecting one of the conference bridges having port capacity for at least n participants as a target bridge for the request; and for each incoming call for the requested conference through the carrier switch: (1) establishing a first incoming connection segment from the carrier switch to the system; (2) prompting the incoming caller for a conference access code; and (3), if the access code received in response to the prompt matches the conference access code, calling the target bridge through the carrier switch to establish an outgoing connection segment from the system to the carrier switch and a second incoming connection segment from the carrier switch to the target bridge; (4) associating the second incoming connection segment with the incoming call; (5) dropping the first incoming connection segment and the outgoing connection segment; and (6) adding the incoming call to the conference on the target bridge. In this manner, each conference call is reliably established on a bridge having sufficient available port capacity without having to designate that bridge in advance of the conference. Customers may still be assigned the same phone number for making reservations or initiating conference calls and load balancing among conference bridges does not have to be performed in advance. The conference access code may, if desired, be assigned in advance.
From a further aspect of the invention, the conference call system includes an interactive voice response (IVR) transfer unit connected to receive incoming calls to the system from the carrier switch. Such an IVR transfer unit is capable of initiating calls through the carrier switch to any of the conference bridges. The system is operated by prompting callers through the carrier switch for the access code and receiving access codes through the carrier switch from callers. From this aspect of the invention, the first incoming connection segment is established from the carrier switch to the IVR transfer unit and the outgoing connection segment is established from the IVR transfer unit to the carrier switch.
From another aspect of the invention, at least one of the conference bridges is interactive voice response (IVR) capable and is connected to receive incoming calls to the system from the carrier switch. Such an IVR capable bridge is also capable of initiating calls through the carrier switch to any of the remaining conference bridges. From this aspect of the invention, callers are prompted through the carrier switch for the access code, and access codes are received through the carrier switch from callers, the first incoming connection segment is established from the carrier switch to the IVR capable conference bridge, and the outgoing connection segment is established from the IVR capable conference bridge to the carrier switch.
From yet another aspect of the invention, if the access code received in response to the prompt does not match the access code, the incoming call is excluded from the conference on the target bridge.
The invention may be more fully understood from the following detailed description, taken in the light of the accompanying drawings and the appended claims.